1. Field of the Invention
The present invention relates to a tape carrier (TAB) used for, e.g., mounting an IC thereon and, more particularly, to a tape carrier having a connection function which enables the connection mechanism of a TAB to be simplified and made further fine by attaching nodules to the conductive pattern portion of the TAB and connecting this pattern portion to that of a mating or another substrate by an adhesive via these nodules.
2. Description of the Prior Art
In the case of a conventional connection of a TAB to another material, the outer lead portion of the TAB is connected to the conductive pattern of an LCD or another rigid substrate by an anisotropic conductive film or soldering. The inner lead portion of the TAB is normally Sn-plated and then heat pressure-bonded to an Au bump portion on an IC, thereby effecting therebetween a bond or connection in the form of an Au-Sn eutectic.
FIG. 7 (Prior Art) is a sectional view showing a tape carrier wherein an IC is connected to the inner leads of a TAB, and an LCD (a liquid crystal display device or a liquid crystal panel) and a rigid substrate are connected to the outer leads thereof. As shown in FIG. 7, the inner leads 708 of a Cu pattern 706 formed on a polyimide film 704 of a TAB 702 are connected to an IC 712 via Au bumps 710. Outer leads 714 are connected to a rigid substrate 716 by soldering. Other outer leads 718 are connected to a liquid crystal panel 722 via an anisotropic conductive film 720. A resin mold 724 is applied to the IC 712 after these connections were made. Reference numeral 726 denotes an insulating resist ink.
There is also known a method for connecting the Sn-plated inner leads of a TAB to an IC by etching the inner leads to form projections on the TAB side, followed by Au-plating the thus formed projections in place of forming the Au bumps on the IC side, and then heat pressure-bonding the IC to the Au-plated projections while forming an Au-Sn eutectic therebetween.
The prior art connection method using an anisotropic conductive film allows the density of leads of a conductive pattern at a connection portion to be generally 5 leads/mm, while no densities greater than this density have actually been used for connection of the conductive pattern, and it is limited to make structurally fine a circuit such as an LCD to which the conductive pattern is to be connected. The density of leads at a connection portion is hereinafter sometimes called "connection density" for brevity.
In addition, a connection method using soldering enables a connection between electrode patterns having a pitch of about 0.5 mm at smallest between adjacent leads; if it is attempted to connect electrode patterns having a pitch not larger than 200 .mu.m are attemped to be connected to each other then a special equipment such as a laser soldering apparatus will be required and, in this case, there is needed a flux which will raise problems as not only as to the number of steps of washing but also its residue.
A method utilizing heat pressure-bonding via Au bumps needs the Au bumps to be formed, resulting in the occurrence of a high cost and poor versatility. In addition, since the heating temperature used in this method is as high as 450.degree. C., the materials and tools to be used are limited. Furthermore, a problem as to a whisker caused by Sn plating is also posed. When projections are to be formed on the side of a TAB, etching for forming the projections will be difficult to achieve if the leads are formed at a fine pitch in the TAB.
Furthermore, when the connection illustrated in FIG. 7 is to be performed, three different apparatuses, i.e., an IC pressure-bonding machine, a soldering apparatus, and an anisotropic film heat pressure-bonding apparatus must be equipped.